1. Field of the Invention
This invention relates, generally, to pressure regulating valves. More particularly, it relates to a pressure regulating valve that harnesses the venturi effect to inject a controlled amount of a liquid chemical into a water stream.
2. Description of the Prior Art
Many applications call for the injection of a chemical in liquid form into a stream of water; the water serves to dilute and carry the chemical into a machine such as a pressure washer, into a container, or onto a surface undergoing treatment.
A typical venturi effect chemical applicator device includes a container having therewithin the liquid chemical to be applied, said container being attached to the end of a water-carrying hose in depending relation thereto, just upstream of a nozzle. A tube is positioned such that its upper end is in fluid communication with the water exiting the hose and its lower end is submerged in the liquid chemical within the container. As water exits the nozzle, it flows past the open upper end of the tube and creates a venturi effect that draws liquid chemicals in the container through the tube and into the water stream exiting the nozzle. Obviously, this well-known, crude construction has few control features. About the only control feature worth mentioning is the ability to roughly control the flow rate of chemicals by adjusting the flow rate of water through the hose.
In commercial applications, there is a need for a device that has a much higher level of control. Adjusting the water flow rate through a hose fails to provide the needed amount of control because water pressure may vary from hour to hour and from minute to minute. Thus, a control device that sets water flow rate at a rate that was acceptable at one moment will not be set properly the next moment if the water pressure changes. What is needed, then, is a control means that injects a predetermined amount of liquid chemicals into a water stream independent of the pressure on the water stream, at a preselected flow rate of water through the nozzle.
One solution to the problem is to provide an injector with a plurality of orifices. For example, U.S. Pat. No. 4,738,541 to Weber discloses an injector having four orifices of differing dimensions. On a low water pressure day, a first orifice is selected as the orifice connected to the chemical container. On a high water pressure day, the last orifice is selected, and the other two orifices are selected on days of intermediate pressure. Obviously, if the water pressure changes while the device is in use, such use must be discontinued and another orifice must be selected.
The ideal device would include a single orifice for a particular flow rate so that those using the device would not have to decide which one to use and would not need to make another selection upon a change in water pressure. The ideal, single orifice device would regulate the flow rate of water entering the device so that instantaneous fluctuations in flow rates would not affect the injection of chemicals into the water stream at the exit end of the device, i.e., the device would operate independently of water pressure fluctuations.
However, when the prior art is viewed as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in this art how such an ideal device could be provided.